1. Field of the Invention
The present invention relates to a data communication apparatus having an error correction communication function.
2. Related Background Art
As a conventional error correction mode, an error correction communication based on a full-duplex communication and an error correction communication based on a half-duplex communication are known. In particular, in the error correction communication based on the half-duplex communication, since a data (image signal) communication sequence and an error correction sequence are sequentially executed, a memory having a predetermined storage capacity or more for holding data is necessary. For example, in an error correction mode (ECM) standardized by the CCITT, a memory having a storage capacity of 64 kbytes must be equipped.
In the above-mentioned error correction communication, in particular, in the error correction communication based on the half-duplex communication, a memory having a predetermined storage capacity or more must be equipped. For example, when a communication in the ECM is to be performed, a memory capacity of 64 kbytes or more must be assured.
A data communication apparatus having a data storage memory normally performs memory transmission or memory reception of data. At this time, when a 64-kbyte ECM memory is left unused, the memory cannot be efficiently utilized as a whole.
However, when the unused memory capacity is smaller than 64 kbytes, a communication in the ECM cannot be performed.
As patents associated with an error re-transmission or re-send operation, U.S. Pat. Nos. 4,829,524 and 4,885,755 are known.
As applications associated with the ECM, U.S. application Ser. Nos. 267,541 (application date: Nov. 4, 1988) and 337,152 (application date: Apr. 12, 1989) are known.
As an application which can solve the above-mentioned problem, and is associated with reception, U.S. application Ser. No. 670,934 (application date: Mar. 18, 1991) is known. However, the present application is associated with transmission, which can solve the above-mentioned problem.